1. Field of the Invention
This invention relates to a method for the removal of a resist film and a method for the production of a semiconductor device and more particularly to a method for the removal of a resist film containing arsenic (As), phosphorus (P) or boron (B), and other inorganic elements and a method for the production of a semiconductor device.
2. Description of the Prior Art
In recent years, methods for the production of semiconductor devices have extensively used a photoresist film as the mask for ion injection or as the mask for dry etching (referred to briefly as "resist film" hereinafter).
By the time that the resist film has been used in production, inorganic elements including arsenic (As), phosphorus (P), or boron (B) which is used for ion injection and aluminum (Al) or titanium (Ti), which is an electrode material to be patterned, have become mingled with the resist film and suffered to form complicated compounds with the material of the resist film which ultimately solidify. The resist film of this nature cannot be easily removed by the well-known method for removing a resist film by the use of an oxygen plasma or ozone and, therefore, there is no alternative but to rely on a complicated treatment.
A method for removing a resist film by the use of sulfuric anhydride (SO.sub.3) has been proposed and has been attracting keen attention recently.
FIG. 9 is a diagram illustrating the construction of a convenient apparatus which can be adopted for the removal of a resist film by the use of sulfuric anhydride (SO.sub.3).
As illustrated in FIG. 9, a SO.sub.3 solution is dropped from a feeder 2 into a flask 1 and is gasified in the flask 1 by heating. The formed SO.sub.3 gas is led into a separate vessel 7 and caused to react with a resist film on a substrate 12 which is heated or kept at room temperature with a heater 11. The SO.sub.3 gas used in the vessel 7 is led into a separate vessel 14 and dissolved in sulfuric acid 17 therein.
When the method mentioned above was tried with samples having resist films, some containing inorganic elements and others not containing any inorganic element, deposited each on the substrate 12, the resist films containing no inorganic element could be easily removed and, more often than not, the resist films containing the inorganic elements could not be easily removed.